Sound recording and reproducing mechanism



Nov. 24, 1942. c. E. YETMAN SOUND RECORDING AND REPRODUCING MECHANISM Filed May 13, 1939 3 Sheets-Sheet l Nov. 24, 1942.

C. E. YETMAN SOUND RECORDING AND REPRODUCING MECHANISM Filed May 13, 1959 3 sheets -sheaf. 2

Q a K g mug v i.

Nov. 24, 1942. c. E. YETMAN SOUND RECORDING AND REPRODUCING MECHANISM Filed May 13, 1959 2 3 Sheets-Sheet .3

will

Patented Nov. 24,1942

UNITED STATES, PATENT OFFICE SOUND RECORDING AND REPBODUUING' MECHANISM ,Chal'les E. Yetlnan, Plllnfleld, N. J.

ApplicationMay 1s, m, Serial No. 273.:

' (oi. Fri-s93) 18 (Haiml.

vices now on the market are provided with turntables which are rotated at a uniform angular velocity and therefore the recordingand reproducing instrumentality will follow the sound groove at varying linear speeds. It is obvious that the smallest circle or lap of the spiral near the center of the record will pass beneath the.

needle during the same time interval as the largest circle adjacent the outer periphery of the disc, even though the largest circle may be sevjeral times the circumference of the smallest circle. For example, if the sound record of a givenword or syllable occupies one inch of the cirfeet a truer or more accurate record of the sound and would hold its cutting edge for a relatively longer time.

Certain .of these advantages have probably been recognized heretofore, and various proposals have been made for attaining them, but machines designed to carry these proposals into effect have failed in actual practice for one reason or another, and no system of constant linear speed sound recording has even been adapted, so far as the applicant is aware.

The present invention is designed to overcome the difficulties which have confronted prior workers in this -field, and in its preferred embodiment contemplates the provision ofa novel and improved recording and/or reproducing device by means of which the angular velocity of the tumtabie upon which the disc is supported is varied continually at a rate which will insure that the relative speed between the surface of the disc and the needle at the point of contact is univ form, Although the other method may be emcumference of the smallest lap or circle near the center of the disc,usually about four inches in diameter,it will occupy about four inches of the circumference of the outermost lap in the 1 case of a sixteen-inch disc. This results in a very considerable waste of space on the record, and gives rise to further disadvantages which may be obviated by the provision of a truly accurate device for providing constant linear speed.

At least three important advantages follow the use of a constant linear speed machine. First, in a disc record of a diameter of sixteen inches, approximately three times the amount. of sound can be recorded thereon as is now possible on theuniform angular velocity type of record of the same size. There results therefrom an enormous saving in record blank material and the elimination of the necessity for the frequent and annoying interruptions for changing records during long musical selections, such as Symphonic recordings comprising several movements. Second, since any given sound would utilize the same space on all parts of the record, the mechanical action of the' cutting or reproducing needle would be the same for that particular sound at all times, and disagreeable variations in tone quality would be eliminated. Third,

the cutting needle running at uniform relative.

speed through the material of the disc would cfployed by suitable modifications of the device, in

this .particular embodiment the record is cut from the center outwardly toward the periphery,

instead of in the opposite direction as in the usual case. because it has been found that the shavings resulting from cutting the record are more likely to fall out of the path of the cutter when this is done. Therefore, means are provided for gradually reducing the angular velocity of the turntable at the same rate that thecutting needle is moved'outwardly from the center of the disc to form the successive spiral laps of the sound grooves. In other words, the rate ofchange in angular velocity is varied in accordance with the radial movement of the needle with respect to the disc.

To attain this continually varying angular velocity. the present embodiment of the invention provides a variable speed drive for both the turntable and the means for feeding the cutting v needle which involves the use of cone pulleys or similar devices, in which the operative connection between the driving and driven elements of the speed change device is moved continually along the effective surfaces thereof at the same accelerated or decelerated rate of advance as the feed of the needle. Although the-dimensions of the variable speed gearing may-be proportionately changed by the interposition of multiplying and diminishing devices, it is preferred that the length of the variable speed driving and' driven elements be substantially the same as the radius of the annular portion of the disc record which is to be inscribed. This provision aids in the proper proportioning of the speed changing elements in direct relation to the distance of the recording needle from the beginning and end of the sound groove. In other words, at any given point which the needle may occupy on the disc the movable operative connection of the variable speed gearing occupies a corresponding point along the surfaces of the elements thereof which will yield the proper angularvelocity of the turntable for effecting the constant speed of that portion of the disc beneath the needle.

The method of computing the rate of change of speed of the mechanism to add or subtract the proper increments for each lap or multiples thereof to attain the desired constant linear speed will now be set forth.

Sound recorders, phonographs, and so-called play-backs as now designed usually run at the rate of '78 revolutions per minute. Some devices have been built to run at the rate of 33 R. P. M. in attempting to make possible an increase in the playing time of the record, but this slow speed gives rise to very serious difliculties in recording and sacrifice of tone quality. In calculating the dimensions and proportions of the illustrative example of the present invention, 80 R. P. M. has been adopted as being sufliciently close to an ideal initial speed, and one from which it is easy to make the somewhat intricate calculations involved in the present speed reducing mechanism.

Also, for purposes of illustration, the device described is adapted to operate upon a disc record of approximately sixteen inches in diameter, the inner smallest circle of the groove of which has a diameter of four inches. If the smallest circle or lap of the spiral of the record is cut at the rate of 80 R. P. M., its running time is three-quarters of a second. Its approximate circumference is 12.6292 inches, and therefore its average rate of linear speed is 16.75 inches per second. The present device is constructed to attain this rate of linear surface speed on all portions of all records which are being cut or played. The laps of the grooves of the record are ,6 of an inch apart, making one hundred laps or approximate circles to the inch of inscribed radius of the disc. On a sixteen-inch record, it is evident that this involves the cutting of six hundred Circles from the four-inch inner circle to the outermost sixteen-inch circle.

To determine the running time and the amount of sound capacity for the record, it is necessary to compute the total length of the sound groove,

and this may be readily done to a very high degree of accuracyby the following method- Since there are one hundred circles in each inch of the record, between the inner four-inch circle and the outer sixteen-inch circle, it is evident that the next larger circle to the smallest four-inch one is .02 inch greater in diameter, and .062832 inch greater in circumference than the four-inch cir-' cle, and this difference is the same for each circle of the disc as compared with the next smaller one. It is convenient to calculate the lengths and running time of the spirals for each inch of surfaced the record. In'calculating these quantities for the first inch, we find that for the ninety-nine circles in the surface from four to six inches in diameter, one should add the numbers from one to ninety-nine and this sum, 4950,

representing the total number of circumference increments for all the subsequent ninety-nine circles, is multiplied by the circumference increment .0628. This gives 31.1018 inches, the total circular length by which theninety-nine circumferences exceed the circumference of the fourinch circle. Since each of the ninety-nine circles have included the circumference of the fourinch circle also, we multiply the circumference of the four-inch circle, 12,5664, by one hundred. This gives 1256.64 inches, and this must be added to a total excess length, 31.1018 inches, the sum being 1567.65 inches, the total length of the oove between the four and six-inch diameters. Since the uniform rate of speed of the record beneath the cutter is 16.75 inches per second, the total running time for this space is 1.55 minutes; Therefore, a program of a length of 1.55 minutes could be recorded in this one inch space on the record. The running time of each of the subsequent five inches of space can be computed in the same way and the results will be as follows:

- Running Circum-f. 1 Tottgl f time car erence 0 eng 0 capacl y C g gg gg j ag ggs: a smallest 100 circumfor sound diameters g y circle in ferences in recording each inch each inch for each of space of space inch of space Inches Inches Minutes Total length 18830. 76 Total running time 19.20 (16" record) If a 33 R. P. M. rate is used, the savings and advantages are proportionately great.

Another object of the invention is to provide means for reversing the movement of the driving mechanism so that the same cycle of movement of the cutting element and the turntable is traversed, but in less time than for the forward movement. Automatically actuated means are provided for disconnecting the drive at predetermined points along the cycle of movement in either direction. These features are important in insuring that the starting point for the "playback is identical with the starting point used in cutting the record, and to provide on each part of the record the same speed in playing back as was used in cutting, thus avoiding distortion in pitch in the reproduced tones.

In this connection, there is also provided novel gaging means whereby the synchronized travel of the cutter and of the variable speed gear connector may be readily determined at any point. This gaging means also enables the determining of starting and ending points for record discs of different sizes and also facilitates the re-synchronization of the belt movement with that of the cutter after the. device has been disconnected, as for working on records of the conventional constant angular velocity type.

A further object is the provision of means for adjusting the change speed gearing to renout of synchronism, as in the case of conventional detachable connections.

A further object of the invention is the provision of novel constructional details in connection with the feed of the cutter and also of the speed change element.

Additional features of novelty and purposes of the present invention will be apparent from the following specification, when read in connection with the accompanying drawings, in which one embodiment of the invention is illustrated by way of example,

In the drawings, 1

Figure 1 is a plan view of a sound recording and reproducing device embodying the principles of the invention;

Figure 2 is a view in' elevation of the same device, a part of the turntable being shown in section; v

Figure 3 is a'vertical sectional view through the device, taken on line 3-3 of Figure l, and on an enlarged scale;

Figures 4 and 5 are transverse sectional views taken on lines 4-.4 of 5-5 of Figure 3, respectively; 1

Figure 6 is a fragmentary sectional view of the coupling and bearing arrangements for certain driving shafts shown in Figure 3;

Figure 7 is a transverse sectional view on a further enlarged scale, and taken on line l-| of Figure 3;

Figure 8 is a similar view showing the gearing in a shifted position; and

Figure 9 is a fragmentary plan view of a clutch element employed in the apparatus.

In the device which has been chosen to illustrate the principles ofthe present invention, the mechanism is supported upon a suitable frame l which comprises a base plate 12 having the feet l3. At each end of the base plate I! there are provided the end plates i4 and I which areconnected by means of the back plate l6. Secured substantially at the center of the base plate i2, as by the bolt and nut connection i], is the hollow post l8 which is adapted to receive the spindle IQ of the turntable 20. Suitable provisions for properly centering and lubricating the spindle are made, and the turntable is a'ccurately balanced so as-to rotate freely upon the post [8 during operation of the machine. Pins 22 are provided near the center-of the tumtable and are adapted to enter correspondingly spaced holes in the disc 24 in order to positively rotate the disc with respect to the recording or inscribing device.

The cutting needle or stylus 25 is carried by the sound box 21 which is of conventional construction and adapted to convert the electrical impulses received from a microphone or amplifying device into vibrations which cause the stylus to cut a corresponding pattern uoon the surface of the disc. The sound box 21 is attached to one end of the angle bracket 28 and is adjustable with relation thereto as by means of the screw 29. The bracket 28 is provided with downwardly turned ears 30 which are rotatably and slidably supported upon the guide rod 3i; the rod 3| being removably supported in the end plate l4, and from the center plate 32 as by means of the clip 33. The outwardly projecting end of the guide rod 3! is provided with a notch '34 into which a spring latch 35, secured to the outer face of the plate I4, is adapted to enter. Secured to the rear end of the bracket 28 is a threaded rod or stem 36 upon which is adjustably box.

carried the counterweight 31 for: the purpose of balancing the box 21 and regulating the pressure of the cutting stylus upon the disc.

For the purpose of guiding the bracket 28 and its attached sound box 2!v along the shaft 3|,

there is provided a carriage or rider 40' which and the projections 30 being spaced by means of the sleeves 46. This arrangement provides means for moving the sound box and also effectively prevents the rotation of the rider 4' lipon the shaft 44.

When the machine is not in operation, or when the movement is reversed so as to bring the stylus back to its original position upon the record, the sound box 21' may be supported in an elevated position by means of the latch or hook element I98 which engages the pin I99 upon the sound The wires 42 lead to the sound box from the terminals 43 secured to the back plate ll of the apparatus and adapted to be connected to the electrical transcribing means which intum is placed in communication with the microphone or other source of the sound to be recorded.

An upwardly projecting arm 48 extends from the rider 4!! and enters the slot 49 formed in the inverted channel bar Eli which extends from the center plate 32 to the end plate I 4 at the top of the frame. Sleeves or rollersii are provided upon the end of the arm 48 forengaging within the slot 49 as the rider moves therealong. The channel bar 50 is rigidly supported in the center plate 32 and the end plate i 4, as indicated at '4 v or continually retarded speed which is necessary to maintain the proper constant linear velocity between the disc 24 and the stylus 25. In order to accomplish this, the screw shaft 44 must be rotated at a continually varying rate and for this purpose the shaft is coupled to-the end of a driving shaft 60. The shafts and 44 are each provided with hollow conical ends which bear upon respective conical ends of the hollow hearing member 62 which is seated in the center frame plate 32. The central portions of the hollow conical ends of the shafts 44 and 60 are squared to receive the squared ends of the coupling pin O3 which rotates within the bore of the' bearing The shaft 63 extends from the plate piece 62. 32 to the end plate IS in which it is provided with trunnion bearing means 65. The shaft III is connected to the power transmission mechanism by mwhanism which will presently be described.

The mechanism for transmitting the driving force from a suitable source of power to both the turntable andthe stylus feed will 'now be described. The source of power, such as an electr c motor (not shown), may be operatively connected to the recording device by means of the belt 10 which passes around the pulley 12 carried by the axle I3 of the input or driving element II of the change speed gearing mechanism, which in this case. comprises a cone of varying taper.

The axle or shaft 18 is provided with tnmnion or shaft supporting bearings I8 and II in the center plate. 32 and in the end plate I8, respectively. The driven element or output member 88 is a complementary shaped cone element which is provided with an axle shaft 82 provided with similar bearing members 88 and '84 in the respective plates 82 and I8, and is disposed in parallel relation with the axle I8 of the driving element I8. The bearing elements I8, 11. 88 and 84 are preferably formed with conical ends received within the respective axles or shafts I8 and 82, just as in the case of the trunnion or shaft supporting member 88, previously described. The two cone pulleys I8 and 88 are operatively connected by means of an endless belt 88 which is adapted to be moved longitudinally of the pulleys to vary the output speed of the gearing. For this purpose, the belt is guided by the rider member or carriage designated generally by the reference numeral 88. This belt guiding rider 88 is best shown in Figures 3 and 4 of the drawings and comprises the tubular element 88 which is threaded upon the hollow tubular shaft 88 which serves a function similar to that of the screw shaft 44 in moving therider longitudinally therealong.

One end of the tubular shaft 88 is seated upon the shoulder or hub 88 formed on the shaft 88 near its left-hand end (Figure 3) and the other end is rotatably seated on the conical end of the bearing member 82 exteriorly of the similar bearmg of the shaft 88. During normal operation of the shaft 85 upon which the flanged spool idlerpulley 88 is adapted to freely rotate. The upwardly extending end of the member 88 is bifurcated as at 81 to receive the guide rod 88 which is secured at one end in the bracket 88, extending forwardly from the rear plate I8, and passes through the plate 82 as at I88. The other member 92 of the rider 88 is provided with an opening I 82 adapted to receive the guide rod 88 and is formed with an upwardly extending arm I84 adapted to enter the slot I88 of the channel member I88, which is similar to the member 88 described in connection with the stylus or needle carrier. Upon the upper end of the arm I84 there are rotatably placed the rollers I88 for engaging within the slot I 88, and for effecting a purpose to be later described.

Between the upper ends of the arms of the members 82 and 83 there' is disposed the flanged guiding pulley or spool I88-which is rotatably and slidably mounted upon the rod 88 and guided between the arms 82 and 88. The belt 88 passes between the flanges of the two pulleys 88 and I88 and in contact with the barrels thereof. It

is obvious from this description that as the beltcarrying rider 88 is moved along the guide rod 88, by the rotation of the threaded member 88, the

be; will be moved along the conical pulleys I8 For obtaining better frictional contact along thetapered surfaces of the cones, two or more narrower belts might be employed instead of one wide one.

The shaft of the driven pulley 88 carries a grooved pulley II8 about which is trained the belt I I2. In order to effect a right-angle change of direction, the endless belt H2 is trained about two small grooved pulleys II 8 which are carried by the shaft I I4 which has bearings in the bracket I I8 secured to the end plate I8. 'The opposite bight of the belt I I2 passes around the pulley I I8 which is rotatably carried by the post I I1 disposed upon the base plate I2. A larger pulley II8 carried by the same post II I and rotating in unison with the pulley H8 is operatively connected by means of a belt I I8 with the pulley I28 carried by the post I2I also secured to the base I2. Upon the upper end of the post I2I there is fixed a friction wheel I28 which bears against the annular ring I28 seated in a groove I21 within the inner periphery of the margin ofthe tumtable 28. The ring I28 is preferably made of suitable friction material whereby a firm and nonsiipping connectionmay be made between the driving mechanism and the turntable. T-he relative proportions of the pulleys H8, H8, H8, and I28, and the dimensions of the wheel I28 are all selected so as to attain the proper speed of rotation of the turntable at a given speed of the output or driven cone 88.

Upon the driven pulley shaft-82 between the cone pulley 88 and the grooved pulley II8 there is fixed the pinion I88 which meshes with the gear I8I carried by the countershaft I82 which is supported by the bracket I88 secured to the end plate I8. Another smaller gear or pinion I35 is fixed to this countershaft I82 and is adapted to be alternatively engaged by the pinion I88 which is rotatably carried'by the shiftable plate I88, which is rockably mounted with respect to, the driving shaft 88. The plate I38 is mounted concentrically with the gear I48 which is fixed upon the shaft 88 so as to rotate therewith in either direction. The pinion I88 is always in mesh with the gear I48 and is adapted to be thrown into mesh with the pinion I88 bythe shifting of the plate I88 as by means of the handle I4I secured thereto, all as clearly shown in Figures '7 and 8 of the drawings. portion of the plate I88, and at the same distance from the center of rotation as the pinion I88, is

the pinion I42 which is also continually in mesh with the gear I48 and is adapted to be alternatively engaged with the gear I48 which is fixed upon the axle I8 of the driving cone I8 at a point between the bracket 88 and the pulley I2. By shifting the plate I88 so that the pinions I88 and I42. are alternatively meshed with the pinion I88 or the gear I48 respectively, it will be seen that the shaft 88 may be driven either at a constant angular velocity from the input shaft or axle I8 of the change speed gearing or at a variable angular velocity from the output axle 82 of the variable speed driven element 88 for purposes which will be described hereinafter. l

When the pinion I88 is meshed with the pinion I88 and the hollow screw shaft 88 is secured to the drive shaft 88 by mean of the set screws 8|, the belt-ca y ng rider 88 will move along the cones in exact synchronism with the stylus-carrying carriag 48, as indicated by the pointer I48 as it moves along the scale I48. The scales I48 and 88 are identical since themovement of the belt carrier 88 and the cutting needle and sounde box carrier 48 are the same in view of the iden- Upon another tical pitch of the threads on the propelling shafts OI) and 44.

Thecaiculation of the dimensions of the cone pulleys I and 80, in order to insure the feeding of the cutting stylus along the disc at the diameter of the other will proportionately increase. Since the belt carrier 86, which effects the variation in ratio of the drive, moves along the cones at the same rate of progress as the cutting needlemoves radially of the disc, it is apparent thatfor each point upon the indicating scale that the cutting disc occupies, there is a definite speed ratio to be developed in the cone drive which will yield the proper angular velocity in the turntable for that particular posltion of the cutting needle. The gear ratio between the output cone 80 and the turntable is so selected that at the start of the recording upon the four-inch circle of the disc, the constant speed cone I5 is rotated at 80 R. P. M., and the variable cone is run at 160 R. P. M. The sum of the diameters of the cones being three inches, the diameter of the variable cone 80 must be one inch, and that of the constant speed driving cone must be two inches.

At this point it may be well to note that in calculating the proper diameters of the cone pulleys, account must be taken of the thickness of the belt, and this thickness added to the diameters of the respective cones in developing the ratios at all points of contact of the belt.

In designing the cones to produce the proper speed ratios at all successive positions of the cutting needle, it is sufficient to select conveniently spaced points, calculate the relative diameters at these points and then connect the resulting circumferences of the respective cones by smooth surfaces. For example, assuming the diameters of the two cones to be two inches and one inch respectively at the start,or at the position of the four-inch circle,the diameters at intervals of one-half inch, or one inch, or even at shorter intervals may be computed and the cones shaped accordingly. The computation of the diameters of the cones for the six-inch circle will illustrate the method. The circumference of the sound groove at this point is 61r or 18.496 inches. Dividing this circumference by 16.755, the standard linear speed in inches per second, gives 1.125 as the number of seconds required for this circle to pass under the cutter at the proper linear speed. This is equivalent to a speed of 53.33 R. P. M. in the variable cone to produce the required speed in the six-inch circle. Thus the diameter of the variable or output c'one 80 at this six-inch point should be 1.285 inches and the diameter of the constant speed driving cone 15 should be 1.715 inches. In a similar manner the proper diameters of the cones for successive positions of the cutting needle may be computed.

A general rule for this computation may be stated thus: Knowing the desired speed in R. P. M., the sum of the diameters of the cones, and the constant speed of the input cone, take such part of the sum of the diameters of both cones as the known constant speed of the driving cone is a part of the sum of the speeds of both cones, and the result is the diameter of the -variable speed or driven cone, which is required to produce the desired speed of the variable. This result, subtracted from the sum of the diameters of both cones, is of course the required diameter of the constant speed cone. The following table illustrates the computation of the dimensions of the variable speed driving means in the particular example illustrated herein, in which the initial speed of the turntableis 80 R. P. M. and the final speed for the sixteen-inch disc is R. P. M.:

Speed oi Speed of Diameters Diameter:

Inch intervals of turntable driven cone of driven oi driv disc (R. P. M.) (R. P. M.) cone com S0. 160. 1. 2. 53. 333' 106. 666 l. 286 1. 715 40. 80. 1. 600 l. 500 32. 64. 1. 667 1. 333 26. 666 53. 332 1. 800 l. 200 22. 857 45. 714 1. DIS 1. 092 20. 40: 2. 1.

This table is merely illustrative of the method of computing the dimensions of the cones and the this maybe accomplished at a much faster speed than the actual cutting operation. To effect this reversal the plate I38 is shifted by manipulating the handle or lever HI, so that the pinion I42 meshes with the gear I43 carried by the input cone shaft 13. Itwill be seen that due to the relative proportioning of the gears and the arrangement of the driving connections, the initial driving means will effect the reverse rotation of the screw shafts and 44 at a more rapid speed than during the opposite movement, and that since these shafts are rigidly connected, the needle 25 will be returned to its initial position in exact synchronism with the return of the belt carrier'86 to the left-hand end of the cones.

In order to throw out the driving connection at predetermined points, for example at the end of the recording space on the given record, the following means are provided. The channel member I05 which serves to guide and calibrate the movement of the belt carrier 86 is mounted in the plates I5 and 32 of the frame of the device so as to reciprocate longitudinally. The narrowed end I50 -of the channel bar I05 is seated in the opening I5I in the frame plate 32, and issecured for limited reciprocating movement therein by means of the pin I52 which passes through the vertical slot I53 in the member. The opposite end of the member I05 is provided with a socket to receive the shaft I55 which pro- Jects through an opening I56 in the end frame I5 and carries three sleeves I60, I6I, and I62,

fixed rigidly thereon by means of set screws. Be-

are laterally offset from each other as illustrated in Figure 9 of the drawings.

Upon the channel bar I there is adjustably secured a stop element I80, as by means of a set screw Iili. This element completely surrounds the bar I05 and is adapted to be contacted by the arm Hit of the belt guiding rider 86 which carries the rollers I06. During the recording or playing movement of the apparatus, the channel bar I05 and its attached devices are in the extreme lefthand position as shown in Figure 3 of the drawings, the pawl I65 is in engagement with the shoulder of notch I12, having been moved .into engagement by means of the lever I, as shown in Figure 'l of the drawings, and the gearing is in mesh for effecting the variable drive. When the belt-carrying member 86 reaches it ultimate position at the end of the recording operation, the carriage will strike the stop member I88 and shift the bar I05 toward the right. When the bar. N35 is shifted, the pawl I65 is moved from above the notch or shoulder I12 and through the influence of the spring I85 which passes through an opening in the stud I88 supported by the plate I5, the shiftable plate I38 is moved to its neutral mid-position, halfway between the position occupied in Figure 7, and that shown in Figure 8. This will cause a cessation of the drive of both the recording or cutting needle and the belt carrier.

Similarly, when the machine is in the rewind or reverse position, shown in Figure 8, the plate E38 is held in proper position for engagement of the pinion M2, by means of the engage ment of the pawl I66 in the notch I13. A stop element I90 is adjustably secured by means of the set screw I9I to the channel bar I05, and is adapted to be contacted and moved toward the left (Figure 3) by the rollers I06 on the belt car- 68. Thus the bar 05 is moved toward the the notch I13 shifted from beneath the pawl Z and the shifter plate I38 is again permitted to assume its neutral position under the influence spring E85. After the automatic disconnecli is effected, the plate I38 may be shifted to reengage the gearing for reversing movement by means of the handle MI.

i. is to be noted that the driving connection either direction may be effected at any time by a manual shifting of the bar I05.

The arrangement above described insures that the belt carrier and the cutter move through identical cycles of movement at all times and insures that the proper angular velocity of the turntable is attained for each radial position of $116 stylus to insure uniform relative linear or surface speed of the disc relative to the stylus at said points,

important in this connection is the employment of completely annular threaded mems for guiding the stylus and the belt shifter elo their respective threaded driving shafts,

from the shaft and a resulting break in byl'lUhlOlliZGd relation is prevented.

eliminate backlash these threaded conthe following device is provided. Each *uiar iembers 4i and 88 are drilled as the reception of the pressure pins I95, '1' 1 upper ends of which bear against the lower side of the screw shafts A l and 90. In order to exert pressure on the pins 595, semi-circular leaf ings are secured as at I91 to the upper sides of the members ii and 88 and their lower ends extend beneath the pins and urge them up- III y inadvertent disconnection of these ele-- wardly and by their reaction tend to cause the upper part of the sleeves or threaded members to engage the threaded shafts more'firmly and thus prevent lost motion or backlash, and effect a more accurate feed.

In Figure 1 of the drawings there is diagrammatically shown a tone arm 200 which is pivotally supported upon a base 2M and is provided with a sound box 202 and an appropriate needle 203 for playing the records which have been cut by the means described. This tone arm needs no feeding means since it will be guided by the contact of the needle with the sound groove on the disc.

It will be understood that various modificatlons may be made in the embodiment illustrated and described herein without departing from the scope of the invention as defined by the following claims.

In the claims-"the term acceleration is employed to indicate either a positive or a negative quantity, that is, either a rateof increase in velocity or a rate of decrease in velocity, according to whetherthe records or discs are inscribed from the periphery inwardly, or from the center outwardly.

Having thus described the invention, what is claimed as new and desired to be secured by Letters Patent is:

1. For use in connection with a recording device of the class described, which includes a rotatable support for a disc to be spirally inscribed and a stylus or the like for inscribing said disc; the combination of a primary driving means for both rotating said support and feeding said stylus radially thereof, transmission means connected between said primary driving means and said support and stylus, and in advanc of the latter two elements, for continually and synchronously varying the angular velocity 01' said support and the rate of radial feeding of said stylus across the record, so that successive portions of the spiral being inscribed pass the stylus at a constant linear velocity, means for connecting said transmission tosaid rotatable support at a single invariable point, and means for automatically interrupting the driving connection in said transmission means at a predetermined time, as upon completion of the record.

2. For use-in connection with a sound recording device of the class described, which includes a rotatable support for a disc to be spirally inscribed and a stylus or the like for inscribing said disc; the combination of a primary driving means for both rotating said support and for feeding said stylus radially thereof, transmission means connected between said primary driving means and said support and stylus for continually and synchronously varying the angular velocity of said support and the rate of radial feeding of said stylus across the record, so that successive portions of the spiral being inscribed pass the stylus at a constant linear velocity, means for reversing .the stylus through the same cycle of movement and out of contact with the disc, whereby the stylus may be brought to the identical starting point upon the disc and the transmission restored to its initial condition for repeating exactly the forward cycle of movement, and means for automatically interrupting the driving connection of the transmission to the stylus only, at predetermined points in both the forward and reverse movements of said device.

3. For use in connection with"a"recording device of the class described, which includes a rotatable support for a discv to be splrally'inscribed and a stylus or the like for inscribing said disc: the combination of a primary driving means for rotating said support and for feeding said stylus radially thereof, transmission means connected between said primary driving means and said support and stylus, and in advance of the latter two elements, for continually and synchronously varying the angular velocity of said support and the rate of radial feeding of said stylus across the record, so that successive portions of the spiral being inscribed pass the stylus at a constant linear velocity, means for connecting said transmission to said rotable support at a single invariable point, and means for adjusting said same transmission means for alternatively rotating said support at constant angular velocity and positively feeding said stylus at a constant speed across the disc.

4. For use in connection with a sound recording device of the class described, which includes a rotatable support for a disc to be spirally inscribed and a stylus or the like for inscribing said disc; the combination of a primary driving means for rotating said support and for feeding said stylus radially thereof, transmission means connected between said primary driving means and said support and stylus for continually and synchronously varying the angular velocity of said support and the rate of radial feeding of said stylus across the record, so that successive portions of the spiral being inscribed pass the stylus at a constant linear velocity, said transmission means including a driving element and a driven element, and a connecting member between said elements for transmitting driving force from the one to the other, said elements being so shaped as to yield varying speed ratios as the connecting member is moved relatively thereto, and gearing for operatively connecting said driven element and said connecting member for moving the latter at a continually varying rate.

5. For use in connection with a sound recording device of the class described, which includes a rotatable support for a disc to be spirally inscribed and a stylus or the like for inscribing said disc; the combination of a primary driving means for rotating said support and for feeding said stylus radially thereof, transmission means connected between said primary driving means and said support and stylus for continually and synchronously varying the angular velocity of said support and the rate of radial feeding of said stylus across the record, so that successive portions of the spiral being inscribed pass the stylus at a constant linear velocity, said transmission means including a driving element and a driven element, and a connecting member between said elements for transmitting driving force. from the one to the other, said elements being so shaped as to yield varying speed ratios as the connecting member is moved relatively thereto, operative connections between the driven element of the transmission and said connecting member for positively moving the stylus and the connecting member at proportionately and continually varying rates of speed.

6. For use in connection with a recording device of the class described, which includes a rotat able support for a disc to be spirally inscribed and a stylus or the like for inscribing said disc; the combination of means for moving said stylus at a continually accelerated speed radially of the disc and means for rotating the disc support at a continually accelerated angular velocity for insuring a constant linear velocity of movement between the surface of the disc and the stylus, said second named means including a change speed device comprising a pair of complementary tapered parallel cone pulleys, one cone adapted to be driven at a constant angular velocity, a connecting member movable along said cones to transmit the driving force from said constant velocity cone to the other or driven cone, and means for positively moving said member in exact synchronism with the stylus moving means, each successive diameters of the cones past which said member moves being so proportioned as to yield velocities of the disc support necessary at the corresponding position of the stylus to give the desired constant linear velocity of the disc beneath the stylus.

7. For use in connection with a recording device of the class described, which includes a rotatable support for a disc to be spirally inscribed and a' stylus or the like'for inscribing said disc; the combination of means for moving said stylus at a continually accelerated speed radially of the disc and means for rotating the disc support at a continually accelerated angular velocity for insuring a constant linear velocity of movement between the surface of the disc and the stylus, both of said means including a common change speed device comprising a pair of complementary tapered parallel cone pulleys, one cone adapted to be driven at a constant angular velocity, a connecting member movable along said cones to transmit the driving force from said constant velocity cone to the other or driven cone, and means for operatively connecting said ,member with the output elementof said change speed gearing so that it is positively moved along said cones at the same accelerated rate as that of the disc support and the stylus.

8. For use in connection with a recording device of the class described, which includes a rotatable support for a disc to be spirally inscribed and a stylus or the like for inscribing-said disc; the combination of a primary driving means for both rotating said support and feeding said stylus radially thereof, variable speed transmission means connected between said primary driving means and said support and stylus for continually and synchronously varying the angularvelocity of said support and the rate of radial feeding of said stylus across the record, so that successive portions of the spiral being inscribed pass the stylus at a constant linear velocity, said transmission means comprising a pair of complementary tapered 'cone pulleys mounted on parallel driving and driven shafts respectively, a belt operatively connecting said pulleys and movable longitudinally of the same for varying the speed ratio of the transmission means, means for positively moving said belt along said cones in exact synchronism with the movement of said stylus radially of the disc, identical graduated scales disposed adjacent the paths of movement of said belt ".nd said stylus respectively, and indicators partaking of the movements of the belt and stylus and adapted to follow the respective scales, whereby the positions of the moving elements may be synchronized.

9. For use in connection with a recording device of the class described, which includes a turntable for rotatably supporting a disc to be spirally inscribed and a stylus or the like for inscribing the disc; the combination of aprimary driving means for both rotating said turntable and feeding said stylus radially thereof,

variable speed gearing disposed between said driving means and said stylus and turntable, and in advance of the latter, for continually and synchronously accelerating the movement of said latter elements so that successive portions of the spiral being inscribed pass the stylus at a constant linear velocity, said gearing comprising a driving shaft rotated at a constant angular velocity by said primary driving means, and a driven shaftjtapered cone pulleys carried by said shafts and operatively connected by a belt, said belt adapted to be positively moved along said pulleys at a continually varied rate, successive diameters of said pulleys traversed by said belt being so proportioned as to yield the proper angular velocity of said turntable at each succes-' sive position of said stylus, shiftable gearing for connecting said stylus and said'belt with said driven shaft for synchronized accelerated movement during the inscribing of the disc and for alternatively connecting said elements with said driving shaft for synchronized movement in the reverse direction for returning the elements to the same starting point.

10. A device as set forth in claim 9 in which traversed by said belt being so proportioned as to yield the appropriate angular velocity of said turntable for each successive position of said stylus, a screw shaft disposed parallel with said pulleys, said belt guiding means being threaded upon said shaft, means detachably connecting said screw shaft with said driven pulley shaft to feed said belt guiding means along the pulleys,

, another screw shaft detachably connected with Zll movement in either direction, and without in-' v terrupting the turntable drive.

12. A device as set forth in claim 9 in which there is provided adJustable means for automatically interrupting the drive of said stylus and belt at predetermined points in their cycle of movement in either direction, said last-named means comprising an oscillatable member carrying two pinions which are continually in mesh with a gear connected with said stylus and belt, and adapted to be alternatively brought into operative engagement with gears driven respectively by said driving and said driven shafts, spring means for biasing said member toward a neutral position in which neither pinion is engaged, catches adapted to engage portions ofsaid member to hold it in positions in which said pinions are engaged with one or the other of their driving gears, means adapted to be tripped by one of said elements for releasing said catches, and means for moving said oscillatable member for re-engaging said pinions.

13. For use in connection with a recording device of the class described, which includes a turntable for rotatably supporting a disc to be spirally inscribed and a stylus or the like for in scribing the disc; the combination of a primary driving means for both rotating said turntable and feeding said stylus radially thereof variable speed gearing disposed between said driving means and said turntable and stylus for continuall'y and synchronously accelerating the movement of said latter elements so that successive portions of the spiral being inscribed pass the stylus at a constant linear velocity, said gearing comprising a driving shaft, rotated at a constant angular velocity by said primary driving means, and a driven shaft, variably tapered cone pulleys carried by said shafts and operatively connected by a belt or the like, means for guidingsaid belt along said pulleys at a continually varied rate, successive diameters of said pulleys said driven pulley shaft, and stylus supporting means threaded upon the second screw shaft, and means for connecting and disconnecting said shafts to and from said gearing.

14. The device as set forth in claim 13 in which means are provided for disconnecting the belt moving screw shaft only from the driving gearing, whereby the turntable may be rotated and the stylus fed at a uniform speed.

15. For use in connection with a recording device of the class described, which includes a rotatable support for a disc to be spirally inscribed and a stylus or the like for inscribing said dis'c; the combination of a primary driving means for both rotating said support and feeding said stylus radially thereof, variable speed transmission means connected between said primary driving means and said stylus and support, and in advance of the latter, for continually and synchronously varying the angular velocity of said support and the rate of radial feeding of said stylus across the record, so that successive portions of the spiral being inscribed pass the stylus at a constant linear velocity, said transmission means comprising a pair of complementary tapered cone pulleys mounted on parallel driving and driven shafts respectively, an endless single loop bel't operatively connecting said pulleys and movable longitudinally of the same for varying the speed ratio of the transmission means, means for positively moving said belt along said cones in exact synchronism with the movement of said stylus radially of the disc.

16. For use in connection with a recording device of the class described, which includes a tumtable for rotatably supporting a disc to be spirally inscribed and a stylus or the like for inscribing the disc; the combination of a primary driving means for both rotating said turnable and feeding said stylus radially thereof, variable speed gearing disposed between said driving means and said turntable and stylus for continually and synchronously accelerating the movement of said latter elements so that successive portions of the spiral being inscribed pass the stylus at a constant linear velocity, said gearing comprising a driving shaft, rotated at a constant angular velocity by said primary driving means, vand a driven shaft, variably tapered cone. pulleys carried by said shafts and operatively connected by a belt, means for positively guiding said belt along said pulleys at'a continually'varied rate, successive diameters of said pulleys traversed by said belt being so proportioned as to yield the appropriate angular velocity of said turntable for each successive position of said stylus, a screw shaft disposed parallel with said pulleys, said belt guiding means being threaded upon said shaft, and means connecting said screw shaft with said driven pulley shaft to feed said belt guiding means along the pulleys.

17. For use in connection with a recording device of the class described, which includes a tumtable for rotatably supporting a disc to be spiral- A means for both rotating said turntable and feeding said stylus radially thereof, variable speed gearing disposed between said driving means and said turntable and stylus for continually and synchronously accelerating the movement of said latter elements so that successive portions of the spiral being inscribed pass the stylus at a constant linear velocity, said gearing comprising a driving shaft, rotated at a constant angular velocity by said primary driving means, and a driven shaft, variably tapered cone pulleys carried by said shafts and operatively connected by a belt, means for positively guiding said belt along said pulleys at a continually varied ,rate, successive diameters of said pulleys traversed by said belt being so proportioned as to yield the appropriate angular velocity of said turntable for each successive position of said stylus, a screw shaft disposed parallel with said pulleys, said belt guiding means being threaded upon said shaft, means connecting said screw shaft with said driven pulley shaft to feed said belt guiding means along the pulleys, another screw shaft detachably connected with said driven pulley shaft, and stylus supporting means threaded upon the second screw shaft, and means for connecting and disconnecting said shafts to and from said gearing, said screw shafts being disposed in axial alignment.

18. For use in connection with a recording device of the class described, which includes a turntable for rotatably supporting a disc to be spirally inscribed and a stylus or the like for inscribing the disc; the combination of a primary driving means for both rotating said turntable and feeding said stylus radiall thereof, variable speed gearing'disposed between said driving means and said turntable and stylus for continually and synchronously accelerating the movement of said latter elements so that successive portions of the spiral beinginscribed pass the stylus at a constant linear velocity, said gearing comprising a driving shaft, rotated at a constant angular velocity by said primary driving means, and a driven shaft, variably tapered cone pulleys carried by said shafts and operatively connected by a belt, means for positively guiding said belt along said pulleys at a continually varied rate, successive d ameters of said pulleys traversed by said belt being so proportioned as to yield the appropriate angular velocity of said turntable for each successive position of said stylus, a screw shaft disposed parallel with said pulleys, said belt guiding means being threaded upon said shaft, means connecting said screw shaft with said driven pulley shaft to feed said belt guiding means along the pulleys, another screw shaft detachably connected with said driven pulley shaft, and stylus supporting means threaded upon the second screw shaft, and means for connecting and disconnecting said shafts to and from said gearing, said screw shafts being disposed in axial alignment, said second named screw shaft being provided with an extension passing axially through said first named screw shaft, and means for connecting and disconnecting said first named screw shaft and the extension of said second named screw shaft, whereby said belt may be held stationary and the turntable rotated at a uniform speed while the stylus is fed across the record.

' CHARLES E. YETMAN. 

